Voltage reference circuit

Abstract

A voltage reference circuit comprising a first reference voltage source, a second reference voltage source, at least one of said first and second reference voltage sources being dependent on temperature, and first circuitry connected to at least one of said first and second reference voltage sources to provide a third reference voltage, said third reference voltage being dependent on temperature.

1. A voltage reference circuit comprising:
 a first reference voltage source; 
 a second reference voltage source, at least one of said first and second reference voltage sources being dependent on temperature; 
 first circuitry connected to at least one of said first and second reference voltage sources to provide a third reference voltage, said third reference voltage being dependent on temperature; and 
 second circuitry connected to at least one of said first and second reference voltage sources to provide a fourth reference voltage, said fourth reference voltage being dependent on temperature, and wherein said third reference voltage temperature dependency is different from said fourth reference voltage temperature dependency. 
 
   
   
     2. A circuit as claimed in  claim 1 , wherein said at least one reference voltage source is directly proportional to temperature. 
   
   
     3. A circuit as claimed in  claim 2 , wherein said at least one reference voltage source is inversely proportional to temperature. 
   
   
     4. A circuit as claimed in  claim 1 , wherein said second circuitry comprises:
 a second circuitry first input; 
 a second circuitry second input; and 
 a second circuitry output, wherein said second circuitry first input is connected to said third reference voltage, said second circuitry second input is connected to said first reference voltage source and said second circuitry output provides said fourth voltage source. 
 
   
   
     5. A circuit as claimed in  claim 4 , wherein said second circuitry further comprises:
 a first gain stage; and 
 a differential amplifier, wherein said differential amplifier is configured to receive the output of the first gain stage and the first input and output a value to the output of said second circuitry. 
 
   
   
     6. A circuit as claimed in  claim 1 , wherein said first circuitry comprises:
 a first input; 
 a second input; and 
 an output, wherein said first input is connected to said first reference voltage source, said second input is connected to said second reference voltage source and wherein said output provides said third reference voltage. 
 
   
   
     7. A circuit as claimed in  claim 6 , wherein said first circuitry further comprises:
 a first gain stage; and 
 a differential amplifier, wherein said differential amplifier is configured to receive at a first input the output of the said first gain stage and output a value to the output of said first circuitry. 
 
   
   
     8. A circuit as claimed in  claim 7 , wherein said first circuitry further comprises a second gain stage, wherein said differential amplifier is configured to receive at a second input the output of the second gain stage. 
   
   
     9. A circuit as claimed in  claim 1 , wherein said third reference voltage temperature dependency is different from said first and second reference voltage temperature dependency. 
   
   
     10. A circuit as claimed in  claim 1 , wherein said fourth reference voltage temperature dependency is different from said first and second reference voltage temperature dependency. 
   
   
     11. A circuit as claimed in  claim 1 , wherein said first reference voltage source is independent of temperature. 
   
   
     12. A circuit as claimed in  claim 1 , wherein said third reference voltage temperature dependency is one of a positive or negative temperature dependency. 
   
   
     13. A circuit as claimed in  claim 1 , wherein said fourth reference voltage temperature dependency is one of a positive or negative temperature dependency. 
   
   
     14. A circuit as claimed in  claim 1 , wherein said third reference voltage is dependent on at least one of:
 said first reference voltage; 
 said second reference voltage; and 
 said first circuitry. 
 
   
   
     15. A circuit as claimed in  claim 1 , wherein said fourth reference voltage is dependent on at least one of:
 said first reference voltage; 
 said third reference voltage; and 
 said second circuitry. 
 
   
   
     16. A circuit as claimed in  claim 1 , wherein said circuit is arranged such that at least one of:
 said third and fourth reference voltages is controllable to have at least one required characteristic. 
 
   
   
     17. A circuit as claimed in  claim 16 , wherein at least one of said third and fourth reference voltage is selected to have a required characteristic by controlling at least one of:
 said first reference voltage; 
 said second reference voltage; 
 said third reference voltage; 
 said first circuitry and said second circuitry. 
 
   
   
     18. An integrated circuit comprising a circuit as claimed in  claim 1 . 
   
   
     19. A method for providing reference voltages comprising the steps of:
 providing a first reference voltage; 
 providing a second reference voltage at least one of which being dependent on temperature; 
 providing a third reference voltage from a first circuitry connected to at least one of said first and second reference voltage sources, said third reference voltage being dependent on temperature; and 
 providing a fourth reference voltage from a second circuitry connected to at least one of said first and second reference voltage sources, said fourth reference voltage being dependent on temperature; wherein 
 said third reference voltage temperature is different from said fourth reference voltage temperature dependency. 
 
   
   
     20. A voltage reference circuit comprising:
 at least two reference voltage sources; 
 first circuitry connected to at least one of said two reference voltage sources to provide a third reference voltage which is dependent on temperature; and 
 second circuitry connected to at least one of said two reference voltage sources to provide a fourth reference voltage which is dependent on temperature, said fourth reference voltage temperature dependency being different from said third reference voltage temperature dependency. 
 
   
   
     21. A circuit as set forth in  claim 20  wherein at least one of said two reference voltage sources being dependent on temperature. 
   
   
     22. A circuit as claimed in  claim 20 , wherein at least one of said two reference voltage sources is directly proportional to temperature. 
   
   
     23. A circuit as claimed in  claim 22 , wherein at least one of said two reference voltage sources is inversely proportional to temperature.